1. Field of the Invention
The present invention relates to a scroll compressor used for air-conditioning apparatus for home or business use and other devices.
2. Background of the Related Art
FIG. 3 is a vertical cross-sectional view showing a conventional scroll compressor of low pressure type.
A closed container 1 has an upper part accommodating a compressor mechanism 2 including a stationary scroll 2a, a movable scroll 2b meshing with the stationary scroll 2a to cause an eccentric revolving motion with respect to this stationary scroll 2a, a thrust bearing 3 supporting the movable scroll 2b, and a bearing member 4 supporting the thrust bearing 3. A shaft 2c of the movable scroll 2b is inserted into an eccentric bearing 6 in a bore 5b provided at an end portion 5a of a crank shaft 5. Thus, a rotational motion of the crank shaft 5 is converted into an eccentric revolving motion of the movable scroll 2b. The crank shaft 5 is associated with an electric motor 7 disposed under the bearing member 4. More specifically, the electric motor 7 includes a rotor 7a connected with the crank shaft 5 and a stator 7b secured, by shrinkage fitting, to the inside surface of the closed container 1. The crank shaft 5 is supported by a main bearing 8a and an auxiliary bearing 8b of the bearing member 4. The closed container 1 has a lower bottom serving as an oil storage 10 reserving lubricating oil 9. Also, the closed container 1 has a side wall on which an intake pipe 23 is installed. According to this structure, the oil storage 10 is subjected to gas pressure of intake side. The bearing member 4 has an oil discharge port 12 allowing the lubricating oil 9 to return the oil storage 10 after lubricating and cooling various components including the main bearing 8a, the auxiliary bearing 8b, the eccentric bearing 6, and the thrust bearing 3. The crank shaft 5 has an eccentric through hole 13 supplying the lubricating oil 9 to various bearing portions, such as the main bearing 8a, the auxiliary bearing 8b, the eccentric bearing 6, and the thrust bearing 3. Furthermore, the crank shaft 5 has a lower end connected with an oil guide 14 by press-fitting or shrinkage-fitting to suck up the lubricating oil 9. An outlet chamber 15, provided between an upper shell 1a constituting a part of the closed container 1 and the stationary scroll 2a, temporarily reserves gas compressed by the compressor mechanism 2 so as to qualify as an outlet muffler. An outlet pipe 16 is provided to discharge the compressed gas out of the closed container 1. A spacer 17 partitions the inside space of the closed container i so that high-pressure gas in the outlet chamber 15 is separated from low-pressure gas acting on the oil storage 10. Through this spacer 17, the stationary scroll 2a and the bearing member 4 are connected with each other by means of bolts. This spacer 17 has an outer peripheral end welded to the inside surface of the closed container 1. The stator 7a has an oil return passage 18 allowing the lubricating oil 9 discharged from the oil discharge port 12 to return the oil storage 10. A reference numeral 19 represents a check valve preventing the movable scroll 2b from causing a reverse rotation in its stop condition. A reference numeral 20 represents an Oldham's ring preventing autorotation and causing the movable scroll 2b to revolve eccentrically with respect to the stationary scroll 2a. A reference numeral 21 represents an intake port provided on the bearing member 4 to introduce low-pressure gas into the compressor mechanism 2. This intake port 21 is placed in the vicinity of the intake pipe 23 connected to the side wall of the closed container 1.
Next, an operation of the above-described compressor will be explained.
Low-pressure cooling medium enters into the closed container 1 through the intake pipe 23. A part of the low-pressure cooling medium cools the electric motor 7 and is introduced into the compressor mechanism 2 from the intake port 21 of the bearing member 4. Revolving motion of the movable scroll 2b with respect to the stationary scroll compresses the gas introduced in the compressor mechanism thereby supplying high-pressure gas to the outlet chamber 15. Thereafter, the compressed gas goes out of the closed container 1 through the outlet pipe 16. After circulating in the refrigerating passage of an air-conditioner, the gas returns to the compressor from the intake pipe 23 so as to realize a well-known refrigerating cycle.
Meanwhile, the lubricating oil 9 is sucked up through the oil guide 14 and then escalated through the eccentric through hole 13 of the crank shaft 5 due to centrifugal force. A part of the lubricating oil 9 is used to lubricate and cool the auxiliary bearing 8b and goes to the oil discharge port 12. Most of the lubricating oil 9 proceeds to the eccentric bearing 6, the thrust bearing 3 and the main bearing 8a successively and is merged into the flow of the lubricating oil 9 coming from the auxiliary bearing 8b, subsequently going out of the oil discharge port 12 on the stator 7b and returning the oil storage 10 through the oil return passage 18 thus constituting a lubricating cycle. In this lubricating cycle a part of the lubricating oil 9 enters, after lubricating the thrust bearing 3, into the compressor mechanism 2 to seal the compressor mechanism 2 and is discharged together with compression gas into the outlet chamber 15.
In such a low-pressure scroll compressor, the lubricating oil 9 entered into the compressor mechanism 2 is discharged into the outlet chamber 15 and sent out of the closed container 1 through the outlet pipe 16. Then, after circulating through the refrigerating cycle, the oil returns to the closed container 1 from the intake pipe 23. Some of the returning oil falls into the oil storage 10 due to gravity, however most is again introduced into the compressor mechanism 2 through the intake port 21 located nearly to the intake pipe 23. This necessitates supply of additional lubrication oil. If such a cycle is repeated, the total amount of lubricating oil consumed, i.e., a summation of original oil and newly added oil, will increase synergistically. It is normally believed that the layout of providing the intake port 21 of the compressor mechanism 2 closely to the intake pipe 23 is advantageous in preventing intake gas from being excessively heated by the electric motor 7. However, this layout is disadvantageous in view of the resulting unexpected increase of lubricating oil since very little oil can return to the oil storage 10 due to natural fall by gravity. In fact, almost all the lubricating oil 9 returned from the intake pipe 23 is directly introduced into the compressor mechanism 2 without returning to the oil storage 10, resulting in reduction of oil amount in the oil storage 10. With reducing oil amount of the oil storage 10, the lubricating oil 9 supplied to various frictional parts decreases proportionally, accompanied by declined reliability. Furthermore, increase of oil introduced into the refrigerating cycle has an adverse effect on the heat exchanger and, therefore, refrigerating ability and efficiency of an air-conditioning apparatus will decrease.